The new post button still has the same issue as seen in the screenshot.

In this particular case only GIF files will help - IE6 does not support PNG transparency and filter: progid:DXImageTransform.Microsoft.AlphaImageLoader won't help here as background-position (well, you can move it as it is absolutely positioned and thus emulate background-position, but that vertical bar in the image spoils everything: the container needs setting overflow: hidden to suppress it, but it breaks the drop-down menu).